PROJECT SUMMARY Multimorbidity is an increasingly prevalent public health concern among middle-aged and older adults. Multiple chronic conditions place a high burden on individuals and their families, leading to elevated rates of hospitalization, disability, and mortality. The spousal tie is a crucial source of health-related influence and support for aging adults with chronic illness. Yet little is known about how individuals with multimorbidity may affect and/or be affected by their spouse in ways that benefit or harm their long-term health. Moreover, few studies have considered multimorbidity in both spouses. Multiple chronic conditions may be particularly stressful when they involve management strategies that are discordant (e.g., reducing cardiovascular risk factors vs. reducing pain) within or between spouses due to heightened support needs. Discordant conditions may also strain limited personal resources and disrupt each partner's self-care routines, resulting in decreased health-promoting behaviors (e.g., physical activity) and increased health-risk behaviors (e.g., alcohol use) that ultimately diminish their health and well-being. This project will advance the literature by examining patterns of multimorbidity within mid- and late-life couples, their long-term implications for psychological well-being and health behaviors, and sociodemographic and psychosocial factors that may buffer or exacerbate these links. The proposed project will draw on data from ten waves (1996 to 2014) of the Health and Retirement Study (HRS), including both members of the spousal dyad. We will explore three specific areas of inquiry: First, we will determine patterns of multimorbidity within and between spouses, focusing on concordance in their management activities and whether patterns vary by sociodemographics. Second, we will evaluate long-term associations between couples' multimorbidity patterns and both spouses' psychological well-being (depressive symptoms) and health behaviors (sleep, physical activity, alcohol use, and smoking). Third, we will identify sociodemographic characteristics (age, gender, race, and education) and psychosocial resources (control beliefs, relationship quality with one's spouse, family members, and friends) that moderate these associations. This project will generate critical information about combinations of multiple chronic conditions that may have lasting effects on health and well-being in aging couples. Research has established that there are consistent associations between one spouse's illness and his or her partner's physical and psychological health; but prior work has placed a near exclusive emphasis on a single chronic condition in one spouse, neglecting an understanding of each partner's multiple conditions and their potential consequences for well- being and health within the marriage. Findings will inform targeted interventions to promote the long-term well- being of older individuals and families managing multiple chronic conditions as well as a more comprehensive approach to the treatment of multimorbidity.